1. Field of the Invention
The present invention relates to a map display apparatus for a vehicle.
2. Description of Related Art
In the prior art, a navigation device is known that displays a map of the region around a vehicle, and that displays congestion information for various roads upon this map. With this type of navigation device there has been the problem that, if the scale of the map is small and the congestion information for each road is displayed upon the map just as it is, then, since the gaps displayed between the roads are narrow, the display becomes complicated and difficult to understand, that is undesirable. Thus, the navigation device described in Japanese Laid-Open Patent Publication No. H10-283589 has been proposed as a device that solves this type of problem. This navigation device calculates the respective level of congestion within each of mesh regions that are set in advance, and changes the hue and/or brightness of the map for each mesh region according to the level of congestion that has thus been calculated. By doing this it is made possible to ascertain simply and easily which regions are relatively congested and which regions are comparatively free, even if the scale of the map is small.
However, with the navigation device described above, although it is possible to display the congestion situation in the mesh units, it is not possible to display the congestion information for each road upon the map in an easily understandable manner.